In a clinical field, a simple method called Point of Care TEST (POCT), which is typified by a self-monitoring of blood glucose level, for example, is spreading. As an example of this method, Patent Document 1 describes a sensing sensor using Quartz Crystal Microbalance (QCM) and discloses a structure that forms a housing space for a sample solution between an upper-side case and a crystal resonator by placing the crystal resonator on a wiring board and engaging the upper-side case and a lower-side case with each other. As a sensitivity enhancing technique of QCM, there are twin sensors that perform a differential measurement. This technique forms two electrodes symmetrically with respect to a channel on one crystal such that the sample solution simultaneously and similarly flows with respect to the electrodes to cancel ambient external noise.
With a sensing sensor, it is desired to narrow a height of a channel to improve a contact ratio of a sensing object to a surface of a crystal resonator. Patent Document 2 describes a structure that configures a height of a channel to 0.2 mm. However, shape variations of a fitted cover may collapse the channel or break the crystal resonator when a channel forming member is pressed. A method that reduces a pressure from the cover that is fitted by narrowing a depressed portion of a seat may be possible, but a sample solution may leak outside the sensor.
Patent Document 3 discloses a method for constituting a piezoelectric sensor by: disposing a piezoelectric resonator on a lower case including an opening portion and a groove surrounding the opening portion, forming protrusions corresponding to a sample solution injection port and the groove in the upper case, and fitting the groove of the lower case and the protrusions of the upper case. However, this document does not mention a height of a channel for a sample solution on the piezoelectric resonator. Accordingly, a problem to be solved differs from the disclosure.